ML20212G545
| ML20212G545 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 10/28/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20212G543 | List: |
| References | |
| NUDOCS 9711060224 | |
| Download: ML20212G545 (6) | |
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UNITED STATES I}
NUCLEAR REGULATORY COMMISSION
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING RENDMENT NO. inR TO FACILITY OPERATING LICENSE NO. DPR-72
(( RIDA POWER CORPORATION. ET AL.
CRYSTAL RIVER UNIT NO. 3 NUCLEAR GENERATING PLANT DOLKET NO. 50-302
1.0 INTRODUCTION
By letter dated March 27, 1997, as supplemented April 3, and May 1,1997, Florida Power Corporation, the licensee for Crystal River Unit 3 (CR-3),
requested an amendment to the plant Technical Specifications (TS). The amendment proposed to:
a) modify the maximum allowable primary-to-secondary leak rate specified in TS 3.4.12.d, Reactor Coolant System Operational Leakage, b) establish requirements for inspecting and dispositioning indications of pit-like intergranular attack (IGA) located in the first span of a known and limited population of tubes in the "B" once-through steam generator (OTSG), and c) make the existing interim reporting requirements regarding steam generator tube inservice inspection (ISI) results tc become permanent.
By letter dated August 20, 1997, the licensee provided clarifications to its previous submittals and modified its original request to specify a more conservative requirement for reporting the results of any OTSG tube inspection to the Nuclear regulatory Commission (NRC)he NRC's original proposed no within 90-days rather than 12 months.
These changes did not affect t significant hazards censideration.
For the proposed codification to TS 3.4.12.d the licensee has requested to set the maximum allowable leak rate through any one steam generator (SG) at 150 gallons per day effect only until the(gpd).
The current TS limit is 150 gpd, but it is in Refuel 11 outage. The proposed amendment would establish 150 c;,J as the permanent limit. The licensee has also requested to establish alternate inspection requirements for examining a specified region in a limited number of tut'es with indications of IGA degradation. The results from these specialized inspections would not be included in the classification of SG tube ISI results in accordance with TS 5.6.2.10.2 provided the results are consistent with those obtained in previous inspections.
In addition to reducing the maximum allowable primary-to-secondary leak rate and establishing specific inspection requirements for a limited population of tubes, the licenset has also requested to permanently establish the inspection reporting requirements included in the CR-3 TS that were to be in effect until the Refuel 11 outage.
9711060224 971028 PDR ADOCK 05000302 P
2 2.0 RACKGROUND Previous 151 of the CR-3 SG tubes have identified a number of tubes with indications of pit-like IGA degradation.
h structive examinations of tubes removed from the SGs have confirmed the presence of this mode of degradation in the span of tubing above the lower tunsheet secondary face and below the first tube support plate characterized as sit-like(i.e., first span). The degradation in the region is IGA, and some indications have been present since 1980. Although tse degradation has existed within a limited number of tubes for several operational cycles, growth rate studies completed by the licensee have concluded that the degradation is relatively stable based on a lack of change observed in the eddy current signal characteristics for the indications.
Prior to the Refuel 9 and 10 outages, the licensee proposed alternative-voltage-based tube repair criteria to disposition tubes with indications characterized as pit-like IGA degradation.- These criteria were approved only on an interim basis and considered other defense-in-depth measures to ensure adequate tube integrity over the next cy.-le of operation.
Prior to the initiation of the next ISI the licensee qualified an eddy current depth sizingtechniquethatappiledtotheIGAdegradationpresentintheCR-3 OTSGs. The licensee proposed to utilize this qualified method of depth sizing the degradation and will disposition confirmed pit-like IGA indications in accordance with the existing depth-based repair limits in the TS (i.e.,
40 percent).
The SG tube ISI requirements for the CR-3 OTSGs are specified in TS 5.6.2.10 OTSG Tube Surveillance Program. The requirements in this TS currently specify an inspection of a three percent random sample of tubes at an interval of at least 12 calendar months not to exceed 24 months. An examination of additional tubes is required if the number of tubes identified as degraded or defective exceeds percent values defined in the TS.
A decrease in the maximum allowable primary-to-secondary leak rate to 150 gallons per minute (gpm) through any one SG was approved in Amendment No. 154 to the CR-3 TS to remain in effect untti the Refuel 11 outage.
3.0 STAFF ASSESSMENT The NRC staff has completed its evaluation of the proposed changes in the primary-to-secondary leak rate limits and the SG tube 151 requirements. The following outlines scope and the conclusions of the staff's assessment.
3.1 Primary-to-Secondarv-Leak Rate-Limit Amendment 154 to the CR-3 TS included a reduction to the maximum allowable primary-tb-secondary leak rate from I gpm (1440 gpd) through all SG tubes to
-15: gpd through any one OTSG. The leak rate limit was reduced in the amendment for one cycle of operation in order to support the licensee's proposed alternate tube repair criteria to disposition indications of IGA in the first span. The revised limit of 150 gpd was consistent with defense-in-depth measures established in other voltage-based SG tube repair criteria.
'The licensee's amendment request dated March 28, 1997, propcsed to make permanent the TS leak rate limit of 150 gpd established in Amendment 154.
3 A permanent reduction in the leak rate limit s)ecified in TS 3.4.12.d will require the licensee to take actions required )y the TS at an earlier stage (i.e., lcwor leak rate) to reduce the measured primary-to-secondary leakage.
Primary-to-secondary leakage may be an indication of a significantly degraded tube.
Under steam line break conditions, leakage through defective tubes in the affected SG could result in a direct release of primary coolant inventory.
The lower leak rate should reduce the total leakage during postulated accident conditions resulting from degraded tubing, and thus minimizing the potential for offsite dose consequences due to the release of the SG secondary side inventory during the event. On this basis, the HRC staff concludes that the licensee's proposal to establish a 150 gpd limit in TS 3.4.12.d is acceptable.
3.2 Reportina Reouirements Staff guidance for the implementation of a voltage-based SG tube repair criteria for Westinghouse model SGs in Generic Letter (GL) 95-05 recommends establishing inspection reporting requirements to the NRC.
S>ecifically, licensees are required to notify the NRC prior to returning tie SGs to service of conditions that could warrant a staff assessment of the tube inspection results.
In addition, licensees are required to submit a more comprehensive o)erational and condition monitoring assessment within 90-days af ter startup.
Taese reporting requirements are necessary to enable the staff to assess whether a licensee can continue to implement a voltage-based repair criteria.
The NRC approved inspection reporting requirements for CR-3 in effect until the Refuel 11 outage.
These requirements were established on an interim basis considering the staff position outlined in GL 95-05.
The methodology proposed by the licensee to address degradation in the first tube span of a number of tubes within the "B" 0TSG will utilize the depth-based repair limits rsther than employ a voltage-based method as in the two prior inspections.
The licensee has requested for future cycles approval of the previously approved reporting requirements establishad for the implementation of the interim tube repair criteria fcr the prior inspection.
The staff finds this change to TS 5.7.2 acceptable in that it will provide the NRC with the results of future inspections.
In the next inspection of the CR-3 SG tubes, the licensee proposes to estimate the depth of pit-like IGA degradation based on data obtained with bcbbin coil probes. Tubes with indications of depths less than the Plugging / Sleeving Limit specified in the TS would be permitted to remain in service.
Sizing the depth of IGA deqradation from eddy current inspection data is a unique i.
application of eddy current technology and is different from the approach used by other utilities.
The general practice employed by other PWR licensees is to plug all indications of IGA degradation confirmed by rotating pancake coil (RPC) probes regardless of the depth estimate provided the bobbin coil probe.
1his plug on detection approach is considered to be a more conservative methodology for inspections in that some tubes may be removed from service with degradation less than the plugging or repair limit. Although the licensee has qualified the eddy current inspection technique for depth sizing, the staff believes that the long range progress of the dispositioning tubes with pit-like IGA degradation as defet.tive or degraded based on bobbin coil eddy current data should be monitored through reporting requirements in a
4 manner consistent with alternate SG repair criteria a) proved by the NRC (e.g.,
GL 95-05). Therefore the staff has concluded that tie licensee's proposal to modify TS 5.7.2, SpecIa1 Reports, is appropriate and acceptable.
3.3 Classification of Inspection Results The CR-3 TS specify a minimum number of tubes selected at random that must be examined with a bobbin coil probe at each ISI.
In addition to the random inspections, TS 5.6.2.10.2 also requires the examination of specified areas that may have a greater potential for tube degradation.
Based on the outcome of these inspections, the scope of the inspections may be expanded to include additional tubes.
For example, if one or more tubes are declared defective, then the inspection is classified as either C-2 or C-3.
Both of these classifications may require the licensee to complete additional random tube inspections.. The purpose of the expanded inspection scope is to account for the increased likolihood that tubes not inspected may also contain similar degradation as identified in tubes selected in the initial sample.
Therefore, expanding the inspection sco)e minimizes the potential of leaving degraded or defective tubes in service t1at were not included in the initial sample inspection.
A number of tubes in the "B" OTSG at CR-3 contain pit-like IGA indications in the first span of tubing. The morphology of this degradation has been confirmed by eddy current examinations and destructive examinations of tubes removed containing these indications. The licensee has concluded based on an evaluation of ISI results completed in the previous plant outages dating back to the early 1980's that the growth of these indications has ceased. The staff has concluded that the pit-like IGA indications have not exhibited any significant progression in recent inspections.
However, it also notes that the potential exists for additional degradation growth in the future.
By letter dated October 1, 1997, the licensee submitted a proposed TS change to address the potential future growth and dispositioning of these IGAs.
The licensee proposed to amend the CR-3 TS to require an examination with bobbin coil and RPC probes during each ISI of the first span of tubing for all tubes identified in the *B" OTSG with pit-like IGA degradation.
The licensee has identified all tubes in the *B" OTSG with these indications.
The identification of tubes with pit-like IGA degradation was completed based on a review of the past inspection results for all tubes within the affected SG.
We licensee would not count the inspection of the first span of these tubes toward meeting the random sam)1e requirements specified in the TS.
Random bobbin coil inspections of tuaes not included in the special interest area will enable the detection of additional pit-like IGA indications in other tubes should the degradation mode become active again.
Indications of degradation detected during the inspections of the first span tube areas would not be included in the determination of the inspection results classification unless modes of degradation other than pit-likt IGA are identified.
The licensee's proposed approach to treat the tubes affected by pit-like IGA as a ssecial interest area include more restrictive inspection requirements than tiose imposed by the minimum sample inspections.
In addition, because each tube affected by this mode of degradation will be inspected during each
5 ISI, additional degradation growth should be detected based on changes in the eddy current signal response. The licensee would remove from service those tubes with pit-like IGA indications with depths measured greater than 40 percent through-wall or that appear to be growing. On these bases, the staff has concluded that it is appropriate to address the pit-like IGA degradation in the "B" O'SG as a special area and thus, exempt the results from the examination of these tubes in the overall classification of the inspection.
Therefore, the staff has determined that the proposed addition of TS 5.6.2.10.2.e is acceptable.
4.0 CONCLUSION
The licensee submitted a proposed changes to the CR-3 TS to modify the primary-to-secondary leak rate limits and the SG tube ISI requirements.
The primary-to-secondary leak rate limit is established in TS 3.4.12.c as 150 gpd through any one SG.
In addition, the modifications and additions to the ISI requirements in TS 5.6.2.10 will enable the licensee to disposition pit-like IGA degradation identified in the first span in a limited population of tubes within the "B" OTSG without requiring an inspection of additional tubes not affected by this mode of degradation.
The staff concludes that these proposed changes are acceptable.
The licensee's amendment request included a proposal to remove the cycle-specific applicability of the SG tube ISI reporting requirements in TS 5.7.2.c, Special Reports that were established on an interim basis prior to-the previous inspections. The staff has concluded that the changes to TS 3.4.12.d and TS 5.6.2.10 along with the licensee's proposed methodology for dispositioning pit-like IGA degradation in the '8" OTSG are consistent with other alternate SG tube repair criteria ap> roved by the NRC.
These often include reporting requirements to inform tie NRC of the results from future inspections. On this basis, the staff has concluded that the licensee's proposal to establish the reporting requirements in TS 5.7.2.c for future l
cycles is acceptable.
5.0 STATE CONSULTATION
Based upon written rotice of the proposed amendment, the Florida State official had no coments.
6.0 ENVIRONMENTAL CONSIDERATION
S The amendments chan e requiremee.t. with respect to-installation or use of a facility component ocated within the restricted area as defined in 10 CFR Part 20 and changes the surveillance requirements.
The NRC staff has determined that the amendments involve no significant increase in the amounts, l
and no significant change in the types, of any effluents that may be released offsite, and that there is no significar.t increase in individual or cumulative occupational radiation exposure.- The Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration, and there has been no sublic comment on such finding (62FR30632).
The amendments also c1ange record keeping or reporting r
- requirements. Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR-SI.22(c)(9) and (c)(10).
Pursuant E
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to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
7.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of these amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
P. Rush, DE/EMCB Date: October 28, 1997 J
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